A radial piston pump unit is already known as the prior art, in which the suction valve is arranged transverse to the vertical axis of the reciprocating piston (DE 102 28 552 B4). The function of this suction valve is to open within a very short time to promote the maximum flow then to close again reliably. In addition the suction valve should be wear-resistant and keep its shape for 1,800 bar with an optimum clearance volume.
These aforementioned parameters can only be fulfilled in the known prior art at high cost and with high constructional outlay.